Saturday, 15 July 2017

Lower surface ice loss because of snow?

Low
surface ice loss on Greenland this year due to heavy snowfall –
consistent with climate warming

We
witness a prevention of enhanced ice sheet mass loss this year (2017)
because of extra snowfall. With more moisture in Earth’s
atmosphere and a pattern in ice cores and elsewhere, the extra snow
is consistent with climate warming.

See
in the graphic below:1.) well above normal snow accumulation on
Greenland starting October 2016 and 2.) a 27 June – 5
July ‘mid summer’ snowfall.

At
this critical point of the year, mid melt season, the surface
mass input (SMB) is 1.2x above normal. By comparison, in the
record loss year 2012, the mass input (the Surface Mass Balance, or
SMB) was roughly 1.2x below normal.

The
extra snow cover and associated high to average albedo is maintaining
the ice sheet. This is good news. And climate change contrarians, do
read to the bottom of this article!

See
graphic below how the albedo over the ice sheet declines through the
year, as normal, then the 27 June to 5 July jump in the blue curve
‘reflects’ (pun intended) mid summer snowfall.

Another
graphic below shows the Greenland whiteness (albedo) map is overall
very blue around the periphery where most melting occurs…

The
punctuation of melt this year is not necessarily enough to offset the
other source of ice mass loss: iceberg calving. Yet, as compared to
the ‘melt pause’ year 2013 (see GRACE satellite data below), I
would not be surprised to see the ice sheet have a no mass loss year
in 2017!

I
found and published a robust Northern Hemisphere air temperature
correlation with Greenland accumulation from ice cores (Box et al.
2013). The relationship has a slope of 7% per degree C
of Northern Hemisphere Air temperature increase, lying on
the Clausius-Clapeyron
vapor pressure curve,
reinforcing that we can expect more snow in a warming climate
(Kapsner et al. 1995) and in agreement with the IPCC AR5 Chapter 12
simulations above.

Weather
or Climate?

Danish
Meteorological Institute: Jesper Rosberg explains, “we have
seen a persistent positive North Atlantic Oscillation this summer and
the jet stream has been very far south of Greenland with very cold
air over the ice sheet, so the precipitation falling this summer has
mostly been snow, rather [than] rain.”

Still,
with global atmospheric absolute humidity rising due to warming, now
all weather systems form in an environment that is wetter and warmer
on average. So, as I see it, it’s simple to expect the average
weather system to dump more precipitation, whether that is rain or
snow.

Negative
Feedback

So,
I’ve presented that in a warmer atmosphere, higher absolute
humidity, increased potential (and actual) precipitation rates… We
see a global pattern of precipitation increase. Now, what may seem
ironic is that soil moisture can decrease in a warming climate
despite increased precipitation. How? evaporation rates increase more
than soil recharge rates. On glaciers in the Arctic, we still get
more net ice loss. Why? The increase in melting is larger than the
increase in snowfall. So, warmer Arctic, more snow, is an example of
a negative feedback.